You would think so, from a technical perspective at least, but this concept was completely unknown to the fuel distributor, including the idea of making sure to buy the correct blend of gasoline to store. Germany is not really a place noted for wide ranging curiosity, so it is possible that his not knowing about it merely reflects the fact that only people that really need to be concerned are those at the refinery.

Ethanol with an RVP of 18 does a better job keeping the RVP low than butane with an RVP of 52.

But because ethanol is slightly polar, and gasoline isn't, the effect of adding ethanol has a greater impact on increasing the RVP. In other words, 10% ethanol will increase the RVP by more than 10% of ethanol's RVP. This is why the EPA had to grant RVP waivers for ethanol blends:

http://www.eia.doe.gov/oiaf/servicerpt/fuel/rvp.html

You can also read here of Dianne Feinstein's efforts to get a waiver from having to blend ethanol:

http://www.senate.gov/~feinstein/05releases/r-epa-oxygenate030905.htm

The California Air Resource Board (CARB) researched this issue at length and found that ethanol-blended gasoline does not help California meet the goals of the Clean Air Act as it relates to reducing ozone formation, particularly during the summertime, and, in fact, ethanol actually increases the emission of pollutants that cause ozone during the summer months.

Bottom line, ethanol is GOOD.

It's hardly that simplistic. It depends on how you make it and how you use it.

This is great topic! (note:...I just crashed, so if this shows up twice, forgive me)

I have a couple of questions...
1) Why is the RVP of ethanol 18? When I look up the vapor pressure ( wiki_ethanol ) it looks like at 100 F the vapor pressure is just over 100 mmHg, or 2-2.5 psi. Am I missing something, or is this a result of the significant deviation that leads to ethanol/benzene azeotropes? Everything I've looked up supports ethanol raising the RVP...except the numbers.

2) All this vapor pressure stuff is dependant on mole fractions, so a very small amount of butane by mass or volume can have a huge effect. Thus a 10% butane mix (mass) will be much greater than 10% by mole fraction, thus much more than 5.2 psi...is there really much butane in any but the coldest gasolines?

3) More of a thermo question. How does decreasing energy content relate to mileage? For example, let's say a hydrocarbon fuel has 100 j/mL, and ethanol has 60 j/mL (made up numbers for easy math). If the unadulterated fuel gives you 20 mpg, what would a 50/50 fuel give you? The energy content would be about 80 J/mL, and a simple calculation would suggest that that translates to 16 mpg (20% reduction).
-my question is whether it is this simple. I suggest that it should be worse, as work that goes into friction and heat will largely stay constant, meaning that the fraction of energy that goes into moving the car takes most of the loss. If half the fuel's energy moves the car then the original fuel used 50 j/mL for friction and heat. If we switched to the mix, 50 J taken from the 80 leaves only 30 for proplusion, for a 40% loss (50 to 30), or a drop in mileage to 12 mpg. Maybe there are advantages (less wasted heat?) that mitigate this?

thanks
-dr

btw...great to hear you live at ASPO, Mr. Rapier